Process for preparing iron or steel sheets such as silicon steel sheets for magnetic uses



Oct. '17, 1939 w. .J/BECKET AL 2,176,602

PROCESS FOR PREPARING IRON OR STEEL SHEETS SUCH AS SILICON STEEL SHEETS FOR MAGNETIC USES Original Filed Feb. 2, 1953 INVENTORS,

0 MOI/v ATTORNEYS.

Patented 0.. 17, 1939 UNITED srA'rEs PROCESS FOR PREPARING IRON OR STEEL SHEETS SUCH ASSILICON STEEL SHEETS FOR MAGNETIC USES Wesley J. Beck and Alva E. Taylor, Middletown, Ohio, assignors to The American Rolling Mill Company, Middletown, Ohio, a corporation of Ohio Application February 2, 1933, Serial No. 654,900

RenewedNovember 15, 1937 and the like for electrical instruments and parts.

There has been considerable effort directed to the forming of continuous strips of silicon steel for use in punch presses, although it has thus far been found impractical to manufacture the high silicon steel in lengths which will be economical to use in punch presses, and to properly cold roll such lengths to give the required surface conditions. Silicon steel is brittle to a degree when cold, is more ductile under a slight rise of temperature, and has a scale that is difficult to deal with. Moreover, silicon steel oxidizes readily, one constituent thereof, upon oxidizing, producing an inert material, namely silicon dioxide, which tends to prevent a welding action. Silicon steel sheets for laminated core work are in addition quite thin in cross-section, running as they do ordinarily between 2 4 and 30 gauge. Thus, while commercially the sheets are produced in short lengths, making the desirability of welding them into lengths for punch press operations obvious, it is not an easy problem to provide a means for welding due to the above characteristics, particularly where a butt weld is attempted. Indeed, we know of no case prior to our work in which a satisfactory butt weld has been produced. Commercial attempts at welding have hitherto produced only lap welds which, while punch press operation may be somewhat facilitated, does not eliminate wastage, or if lap-welded sections are employed in transformer cores or the like, produce cores of less efiiciency, and lower space factor.

It is an object of our invention to produce silicon steel in strip form in which the individual pieces are joined by butt welds. The welds must be flexible, so that the strip may be coiled for shipment arid handling in the slitters, and in the punch presses. The welds must be strong and capable of withstanding repeated strains.

These alloys are readily oxidizable, and a method of welding would suggest itself which departed from oxidizing conditions. It is found, however, that the ordinary electric are or resistance welding under reducing conditions or under atmospheric conditions, will not be satisfactory.

To resort to gas welding would at first consideration appear to be impractical. The metal is so thin that an attempt to fuse the edges together in a butt weld, which most be smooth,

ing temperature would seem to be impractical, ex-

cept with the attendant danger of puncturing the product at the weld line.

After a great deal of experiment, however, we have discovered that standard silicon steel sheets of considerable width (regular rolling mill widths for sheet metal being well within the range) can be welded by a gas, and that the weld, though formed of silicon steel (the base metal), will be flexible enough to submit to the required bend-' ing for coiling, decoiling and the like; and will in addition be strong and permanent, without .any breaks along the weld line. a

We have been able commercially to produc butt welds having these desirable characteristics in thin silicon steel sheet material by that series of process steps of which we shall now describe an exemplary embodiment. Reference is made to the accompanying drawing which shows in somewhat diagrammatic form a set of conditions, such as is contemplated by our invention, surrounding the weld as it is being formed. It will be understood that we are not restricted specifically to the showing of this drawing.

We find that in welding silicon steel sheets end to end, by a butt weld, we do not gain any advantage by the use of a flux or solder. To gain a clean edge for the weld, we merely shear the product and neglect the presence of such scale as may be present along the faces adjacent to the cut edges.

We find also that it is absolutely necessary to have parallel edges that can be butted together at all points, and that prior to welding, the edges must be butted and held closely in to complete contact. Any departure from this will resuit in a punctured product.

In the next place, it is necessary to exclude oxygen from the weld as it is being formed, on the side of the sheets opposite the side being treated by the welding flame. This may be done in a number of ways as by means of a non-oxidizing gas, but we prefer to employ for this purpose,

means which support the metal sheets below the butted joint, by which we mean a member which is continuous across the line of weld, and is coplanar with the sheets. This is to be distinguished from merely supporting the sheets adjacent the butted joint, which also is desirable. Means to support the actual edges of the sheet below the butted joint are quite desirable since such means not only excludeoxygen from the weld, but also tend to prevent the blowing of holes in the weld. Again, such support helps to prevent the buckling oi the edges adjacent the line of weld.

A conductivemetal support would, however, prevent the development oi" sufficient heat for the weld. We therefore provide as a support some material less conductive of heat, such as piece of carbon, or we raise the temperature of the backing bar to a point approaching the temperature of the weld, hereinafter se' iorth.

Our best results have been attained with an oxyactylene torch. "foils must be arranged to give a neutral flame, since an oxidizing flame will oxidize the metal, and a reducing flame will not give sumcient heat to melt it. When the sheet edges have been trimmed square and placed in close and complete abutment, the oily-acetylene torch with neutral flame is passed quite rapidly across the butt joint.

Since the metal is thin and the flame very hot,

there is a tendency of the sheets to buckle even during the rapid passage of the welding flame across the joint. In order to overcome we find it best to hold the sheetsdown by members lyingacross them and very close to the joint itself.

If the weld is formed as above noted, while the pieces are warm, the strip as it is formed is passed between rolls, which will flatten and roll out any excessive metal at the joint. rolling is not a necessity, but it is quite desirable. It cannot be done while the metal is cold, however, and unless the rolling is done while the heat from welding is still in the metal, the strip will have to be heated up somewhat before rolling.

Proceeding in the manner above outlined, we have produced with very great saving to the manufacturers of electrical apparatus, strips of silicon steel of indeterminate length, made from the ordinary steel mill widths of silicon steel sheets in gauges required for laminations of electrical apparatus. Our weld is formed with: out any appreciable variation in electrical properties of the pieces welded; and subsequent heat treatments will not destroy the weld, which, while it appears to be somewhat more flexible than the metal itself, does not give way under heat, and is as tough as or tougher under bending strain than the metal. Pieces for electrical apparatus can be stamped or punched out so as to include the welded joint in the stamplngs withoutany appreciable deterioration in the electrical propertles of the stamping or punching. As can readily be appreciated, this saves for the manufacturer quite a large portion of what has formerly been waste from the stamping operation.

In the drawing we have indicated an exemplary apparatus'with which our process may be practiced. We have shown the sheets I and 2, with sheared edges held in exact abutting relationship by upper clamping jaws 8 and 4, and lower clamping jaws and 6, a pair of said jaws being located on either side and adjacent the butted edges. The sheets are supported beneath clamp members 3 and t the butted joint by a backing bar indicated generclly at 9. This may be oi! a substance of low heat conductivity; but if made 01' metal, we prefer to provide it with an inset heating bar ID of electrically resisting alloy, set in an insulating substance II. Electric current may be employed to raise the temperature of the bar M. We are not restricted to this construction, however since metallic backing bars otherwise heated may be employed. It will benoticcd that the top of the backing bar 9, and or the heating but ill, form 2. plane surface which supports the sheets beneath the actual edges thereof and below the buttecl joint. It is preferable to press the backing her up into tight contact with the sheet edges, for which purpose, in one embodiment of our inventlon, we mount the backing bar slldably in a member l2, and advance it against the sheet edges underpressure. Preferably the upper extend slightly over the edges of the backing bar as shown. The function of the backing bar in excluding oxygen from. the weld on the side opposite the flame will be clear. The welding is done by means of a flame i from the torch 8.

While we have devoted our attention chiefly to the welding of silicon steel sheets, in which specinl problems are involved, we find that we can weld in the same manner other alloys of iron, such as alloys high in nickel content or plain steel sheets where the butt joint is de.slrable as for punch press work, and the metal is quite thin and likely to run under the weld.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent, is:

i. That process of butt welding silicon steel sheets, which consists in cutting the edges to exact parallelism, clamping the edges into complete abutting contact throughout the joint to be welded, supporting the actual edges of the sheets beneath the butted joint, and welding the metal of the sheets together by means of a neutral gas flame, while excluding oxygen from the weld upon the side opposite the flame.

2. That process of butt welding silicon steel sheets, which consists in cutting the edges to exact parallelism, holding the edges in complete abutting contact throughout the joint to be welded, and welding the metal of the sheets together by means of a neutral gas flame, the actual edges being supported during the welding upon the side away from said flame by a poorly conductingplanar surface as a backing plate, said plate extending across the joint and closely adjacent thereto to exclude oxygen therefrom.

3. That process 01' butt welding silicon steel sheets, which consists in cutting the edges to exact parallelism, holding the edges in complete abutting contact throughout the joint to be welded, and welding the metal of the sheets together by means of a neutral gas flame, the actual edges being supported during the welding by substantially uniplanar means on the opposite side of said flame, extending across the joint and closely adjacent thereto to exclude oxygen therefrom, the ends of said sheets being held down against buckling along lines closely adjacent to the butt Joint.

4. That processof butt welding silicon steel sheets, which consists in cutting the edges to exact parallelism, holding the edges in complete abutting contact throughout the joint to be welded, and welding the metal of the sheets together by means of a neutral gas flame, the actual edges being supported during the welding by a surface adapted to be raised, without substantial deterioration, to 'a temperature approaching that of the welded metal, said surface being disposed onthe side away from said flame, and being continuous across the joint and co-planar with the sheet edges so as to exclude oxygen from the line of weld.

5. That process of butt welding silicon steel;

extending across the joint in co-planar relationto the sheet edges and closely adjacent thereto to exclude voxygen therefrom and adapted tobe raised, without substantial deterioration, to, a

temperature approaching that of the welded metal, and rolling the metal at the welded joint while maintaining the heat of the weld.

6 .'That.process of butt welding silicon steel sheets, which consists'in cutting the edges to exact parallelism, holding the edges incomplete abutting contact throughout the joint. to be' welded, andwelding the metal of the-sheets together by means of a neutral gas flame, the actual edges being supported duringthe welding upon a carbon backing plate, disposed on the side away from said flame, being continuous and co-planar across said jointand adapted to exclude oxygen from said weld, and rolling the welded joint whil maintaining the heat ofthe'weld. 7. That process of butt welding thin silicon steel sheets which comprises cutting. the edges of sheets to exact parallelism, holding the edges in complete abutting and co-planar contact throughout the joint to be welded and welding said sheet edges together by a neutral flame which protects the weld from oxidation upon one side, supporting the actual edges of the sheets by means on the other side 01. said weld in the nature of a backing bar having a surface extending across and in co-planar relationshipto said edges upon the side opposite to said flame, whereby oxygen is excluded from the weld, and heatsheets end to end so as to make completely usable .strip' stock of indefinite'lengthior punching,

stamping and the like, the. joining being accom plished by butt welding while the edges of successive sheets are held parallel and in butted relationship, which comprises bringing a smooth,

flat backing member against. the butted edges' and marginal portions of the sheets upon one sideof said butted sheetsso as'both to support the metal at the line of weld and to protect the metal upon said one side irompxidation, making a weld by applying a. neutral gas flame to said edges on the other side of said butted sheets,;

and during said welding, raising the temperature of said backing member to a temperature approaching, that oi the weld;

10. That process of joining thin silicon steel sheets end to end so as to make completely usable strip stock of indefinite length for punching, stamping and the like, the joining being accomplished by butt welding while the edges of suc- 'cessive sheets are held parallel and in butted relationship, which comprises bringing, a smooth,-

flat backing member against the butted edges and marginal portions of the'sheets upon one side of said butted sheets so as both to support the metal at the line of weld and to protect the metal upon said one side from oxidation, making a weld by applying a neutral gas flame to said edgeson the other side of said butted sheets, and during said welding, raising the temperature of said backing member to atemperature approaching that of the weld by applying electric current to said backing member to raise the temperature thereof.

' WESLEY J. BECK.

ALVA E. TAYLOR 

